1. Field of the Invention
The present invention relates in general to an optical repeater device and, in particular, to an erbium-doped fiber amplifier that uses a flexible optical circuit to amplify an optical signal.
2. Description of Related Art
An erbium-doped fiber amplifier (EDFA) is basically an optical repeater device that functions to boost the amplitude of optical signals traveling through a fiber optic communications system. In particular, the EDFA incorporates a variety of components including a laser diode, a multiplexer and an optical fiber which is doped with the rare earth element erbium. The laser diode emits light having an infrared wavelength of 980 nm or 1480 nm that is passed through the multiplexer into the erbium-doped optical fiber. The emitted light excites the erbium atoms in the optical fiber. Then when an input optical signal having a wavelength of between 1530 nm and 1620 nm passes through the multiplexer and enters the optical fiber it stimulates the excited erbium atoms to emit photons at the same wavelength as the input optical signal. This action amplifies the input optical signal to a higher power by effectively boosting the amplitude of the input optical signal. Examples of two traditional EDFAs 100 and 200 are briefly discussed below with respect to FIGS. 1 and 2.
Referring to FIG. 1 (PRIOR ART), there is a block diagram illustrating the basic components of a traditional EDFA 100. The EDFA 100 includes a variety of components including a laser diode 102, a multiplexer 104 and a custom-designed bobbin 106 that holds a predetermined length of erbium-doped optical fiber 108. The optical fiber 108 which can be relatively long (e.g., xcx9c50 m) is wrapped around the bobbin 106 before being placed in a package 110. The package 110 contains the various components that make-up the EDFA 100 including the laser diode 102, the multiplexer 104 and the bobbin 106. In operation, the EDFA 100 receives an input optical signal 112 that is coupled by the multiplexer 104 along with the light from the laser diode 102 into the erbium-doped optical fiber 108 which becomes excited by the light from the laser diode 102 and outputs an amplified optical signal 114.
Unfortunately, there are a number of disadvantages associated with using the bobbin 106 to hold the optical fiber 108. First, the bobbin 106 needs to be custom designed so it can fit within the package 110. Secondly, the bobbin 106 itself is bulky and restricts the overall outline of the package 110. Thirdly, the optical fiber 108 may be stressed if the optical fiber 108 is wrapped to tight around the bobbin 106. As such, the custom-designed bobbin 106 delays and adds complexity to the design of the EDFA 100 and can also adversely affect the operability of the EDFA 100.
Referring to FIG. 2 (PRIOR ART), there is a block diagram illustrating the basic components of another traditional EDFA 200. The EDFA 200 includes a variety of components including a laser diode 202, a multiplexer 204 and a predetermined length of erbium-doped optical fiber 206 that is held together by a fastener 208 including, for example, wire, string, tape, or glue (shown and described below as three wires/strings 208). Prior to being inserted into the EDFA 200, the optical fiber 206 which can be relatively long (e.g., xcx9c50 m) is wrapped around a customed-designed fixture 210 (e.g., bobbin) (see exploded view). Once the desired length of optical fiber 206 is wrapped around the fixture 210, then the optical fiber 206 is removed from the fixture 210 and the loose coil of optical fiber 206 is contained by the wire/string 208 (see exploded view). The optical fiber 206 that is held together by the wire/string 208 is then placed in a package 212. The package 212 contains the various components that make-up the EDFA 200 including the laser diode 202, the multiplexer 204 and the optical fiber 206. In operation, the EDFA 200 receives an input optical signal 214 that is coupled by the multiplexer 204 along with the light from the laser diode 202 into the erbium-doped optical fiber 206 which becomes excited by the light from the laser diode 202 and outputs an amplified optical signal 216.
Unfortunately, there are a number of disadvantages associated with using the fixture 210 to wrap the optical fiber 206 and for using the wire/string 208 to contain the optical fiber 206. First, the fixture 210 needs to be custom designed such that the coil of optical fiber 208 has the desired diameter so it can fit within the package 212. Secondly, the optical fiber 206 may be stressed if the optical fiber 206 is wrapped to tight around the fixture 210. Thirdly, the optical fiber 206 may be stressed if the wire/string 208 is wrapped to tight around the optical fiber 206. As such, the custom-designed fixture 210 delays and adds complexity to the design of the EDFA 200 and the use of wire/string 208 to hold the loose coil of optical fiber 206 can adversely affect the operability of the EDFA 200. Accordingly, there is a need for a new way to wrap and support the optical fiber that is placed inside the package of an EDFA. This need and other needs are satisfied by the flexible optical circuit and the method of the present invention.
The present invention includes an erbium-doped fiber amplifier, a flexible optical circuit and a method for fabricating the flexible optical circuit. Basically, the erbium-doped amplifier includes a laser diode, a multiplexer and a flexible optical circuit. The flexible optical circuit in one embodiment includes a predetermined length of optical fiber that is placed onto and secured to a partially flexible sheet of material. Several different embodiments of the flexible optical circuit are described herein. In operation, the erbium-doped amplifier receives an optical signal that is coupled by the multiplexer along with a light from the laser diode into the erbium-doped optical fiber which becomes excited by the light from the laser diode and outputs an amplified optical signal.
A more complete understanding of the present invention may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein:
FIG. 1 (PRIOR ART) is a block diagram illustrating the basic components of a traditional EDFA;
FIG. 2 (PRIOR ART) is a block diagram illustrating the basic components of another traditional EDFA;
FIG. 3 is a block diagram illustrating the basic components of an EDFA in accordance with the present invention;
FIG. 4 illustrates a top view and a cross-sectional side view of a flexible optical circuit that can be used in the EDFA shown in FIG. 3;
FIG. 5 is a flowchart illustrating the basic steps of a preferred method for fabricating the flexible optical circuit shown in FIG. 4;
FIG. 6A illustrates a top view and a cross-sectional side view of a first embodiment of the flexible optical circuit that can be used in the EDFA shown in FIG. 3;
FIG. 6B is a flowchart illustrating the basic steps of a preferred method for fabricating the first embodiment of the flexible optical circuit shown in FIG. 6A;
FIG. 7A illustrates a top view and a cross-sectional side view of a second embodiment of the flexible optical circuit that can be used in the EDFA shown in FIG. 3;
FIG. 7B is a flowchart illustrating the basic steps of a preferred method for fabricating the second embodiment of the flexible optical circuit shown in FIG. 7A;
FIG. 8A illustrates a top view and a cross-sectional side view of a third embodiment of the flexible optical circuit that can be used in the EDFA shown in FIG. 3;
FIG. 8B is a flowchart illustrating the basic steps of a preferred method for fabricating the third embodiment of the flexible optical circuit shown in FIG. 8A;
FIG. 9A illustrates a top view and a cross-sectional side view of a fourth embodiment of the flexible optical circuit that can be used in the EDFA shown in FIG. 3;
FIG. 9B is a flowchart illustrating the basic steps of a preferred method for fabricating the fourth embodiment of the flexible optical circuit shown in FIG. 9A;
FIG. 10A illustrates a top view and a cross-sectional side view of a fifth embodiment of the flexible optical circuit that can be used in the EDFA shown in FIG. 3;
FIG. 10B is a flowchart illustrating the basic steps of a preferred method for fabricating the fifth embodiment of the flexible optical circuit shown in FIG. 10A;
FIG. 11A illustrates a top view and a cross-sectional side view of a sixth embodiment of the flexible optical circuit that can be used in the EDFA shown in FIG. 3; and
FIG. 11B is a flowchart illustrating the basic steps of a preferred method for fabricating the sixth embodiment of the flexible optical circuit shown in FIG. 11A.